Many construction machines are provided with a work implement that is attached to the front or rear portion of the machine. The work implement is typically connected by some type of lift arm arrangement that is controlled by the operator to manipulate the implement. In machines such as wheel loaders, a lift arm arrangement is provided that typically includes a pair of lift arms that extend between the machine and a bucket or other work implement. At least one hydraulic cylinder extends between the frame and the lift arms to pivot the lift arms with respect to the machine. A cross brace is normally secured between the two lift arms at a location that is positioned between the work implement and the machine frame. A tilt arrangement of one or more levers and at least one hydraulic cylinder is normally provided to pivot the implement with respect to the lift arms. Support for the tilt arrangement is provided by the cross brace through a plurality of brackets that extend from the cross brace. Since the work implement is spaced a substantial distance from the machine frame and generally is required to lift substantial weight during normal operation, the lift arm arrangement is subjected to severe loading of various types and from multiple directions.
In order to accommodate such severe loading, the lift arms have typically been constructed of very substantial welded fabrications. In order to accommodate torsional loading, the cross brace is formed of a tubular member that is welded to the inner face of each lift arm to prevent twisting of the lift arm arrangement. Since the lift arm arrangement is a welded fabrication, it inherently includes severe concentrations of stress between the connected components. This is especially true at the interface between the lift arms and the cross tube. In order to allow for the stress concentration at this junction, in which the components are positioned at 90.degree. from one another, the size of the components in these areas must be increased as is the weld that secures them together. These large welds cause distortion between the members connected by the weld. Also large welds cause residual stresses which require a stress relieving process to attain satisfactory life. Further, since the weld between the cross tube and each lift arm is located at their juncture on the inner side of the lift arm, there is often not enough room allowed to take advantage of robotic welding techniques. Therefore the weld is done manually, which is a laborious time consuming operation. The end result is a lift arm arrangement that is exceptionally heavy that requires several labor intensive weldments to construct. This not only requires more counterweight at the opposite end of the machine to offset the massive lift arm structure, the added weight and manufacturing requirements adds substantially to the cost of the components.
The subject invention is directed to overcoming one or more of the problems set forth above.